Segment, Geographic and Product Information - Geographic Information Regarding Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 473,747	$ 455,042	$ 1,553,773	$ 1,577,335
U.K.
Revenues:
Total revenues	193,704	192,271	646,496	657,367
U.S.
Revenues:
Total revenues	120,161	113,551	393,480	402,944
Asia
Revenues:
Total revenues	75,049	75,892	233,416	240,080
Other Europe/MEA
Revenues:
Total revenues	47,282	36,275	156,053	149,420
France
Revenues:
Total revenues	22,159	23,905	77,439	84,126
Other Americas
Revenues:
Total revenues	$ 15,392	$ 13,148	$ 46,889	$ 43,398